Relay



May l, 1945 F., PERRIN ETAL 2,375,130

pppppfqqqqf- Ea `505 5i@ 5l j 52 zo n ATTORNEYS May 1, 1945.

F. PERRIN ET AL RELAY Filed Deo. l2, 1942 2 Sheets-Shea?l 2 ATTORNEYS Patented May l, 1945 RELAY' Francis Perrin and Boris Pregel, New York, N. Y.,

assignors to Canadian Radium & Uranium Corporation, New York, N. Y., a corporation of New York Application December 12, 1942, Serial No. 468,846

7 Claims.

Oui` invention relates to a new and improved relay.

Said relay may be of the delayed-action type, so that .the desired result or relay eiect will be produced at the end of a substantial predetermined period after the relay has been primed or set into operation. Said relay may produce said desired result quickly after it has been set into operation.

The relay includes one or more control elements or control units. These units have a variable conductivity regulated independently o f heat, and without the use of mechanical devices. Such unit may conduct current, either by ionization or by electronic emission. The ionization can be produced by radio-active material. Electronic emission can be secured by a photo-electric cell which operates without a heated cathode. For example, such photo-electric cell can have an unlieated caesium cathode, which will emit electrons at normal temperature of about 20 C. under the action of light.

The relay can be used for various military and industrial purposes, such as to produce delayed explosions of bombs, including aerial bombs.

The principal objects of the invention are to produce a simple and durable relay, which can be made at relatively low cost, and to magnify the minute ionization current or electronic current which is produced in the control unit or units, Without the use of electronic tube ampliiiers` Numerous additional objects of the invention are set forth in the annexed description and drawings, which illustrate various embodiments.

The drawings are wholly diagrammatic.

Fig. l illustrates one embodiment of our invention in its simplest form. This. utilizes a single resistance unit which has a falling characteristic, and a single control unit.

Fig. 2 illustrates a second embodiment, which utilizes two such resistance units and a single control unit. This delivers more energy than the embodiment of Fig. 1.

Fig. 3 illustrates a third embodiment which has two raid rsistance units and two said con? trol units.

(Cl. Z50-83.6)

relation between lapse of time and ionization,

in using gaps in which a gas or mixture of gases produced by a long-life radio-active substance,

such as radon which is produced by radium.

Fig. 7 shows another embodiment, in which a photo-electric cell is used. y

The invention Will first be described with ref- -erence to the use of relay units which utilize Aor other bombs.

One of the most easily available radio-active substances is radon, which is a gaseous emanation of radium. The half-life period of radon A is approximately Afour days, the exact length of said half-life period being more accurately designated as about 3.8 days.

By using different radio-active substances which have different respective half-life periods, we can produce delays in the action of the relay between a few days and a few weeks. The period of delay depends upon the choice of the radioactive substance, since respective radio-active substances have respective different half-life periods.

We can also secure different periods of delay, while using a single radio-active substance which may be radon or many other radio-active substances. In such case, we use different applied voltages and different resistances in the circuit,

- so that the period of delay can be varied from Fig. 4 illustrates a fourth embodiment, which utilizes two ionization chambers which have conductive metal walls.

Fig. 5 illustrates another embodiment which utilizes a pair of capacitances, a pair of said resistance units, and a pair of said control units.

Fig. 6 shows the curves which illustrate the about 50% to 400% of thel half-life period of the respective radio-active substance. By using different radio-active substances, the period delay can be controlled from a few hours to several months. Amongst other radio-'active substances,

we include, radon, radium A & B & C which is tivity of a radio-active substance is to measurethe decrease of anionization current which is produced in a gas which islocated in an electric ileld and which is subjected to the radiation of the radio-active substance.v However, such ionization currents are very small. For example, if

' a fraction of a milligram of radium is used, the

ionization current is'only a small fraction of a Y -microa.mpere. The use of much larger quantities of radium or the like would be prohibitively ex-1 invention is not limited to using the decrease in such ionization current.

Fig. 1 shows a source of electric current I which may be of any type. It may consist of anumber ofdry cells which are connected in series, in order to provide a voltage of .100 volts at the terminals 2 and .3 of said source I. It is to be understood that any details which are stated herein, in order to give one or more working examples, are merely illustrative and that the invention is not limited to the same. The terminal 2 is connected through a resistor II to one terminal 5 of a condenser or capacitance 4. The terminal l of the source I is connected to the other terminal 8 of said capacitance l. In the example stated herein, the resistance of the resistor II is about 1,000 megohms. The capacity of the seriesconnected dry cells of the source I can be very small. The capacity of the condenser 4 is about 0.1 microfarad. The dielectric of the condenser l should have maximum resistivity, in order to minimire any leakage current through said condenser. It is therefore preferable to provide a mica dielectric for said condenser l.

'I'he terminals 5 and 8 of the condenser I are respectively connected to the terminals 1 and 9 of an ionization chamber 50 which -has spaced electrodes E, which are separated by gap 50a.

The electrodes E are connected to the circuit at the points 1 and 9.- Said ionization chamber 50 may contain air at normal atmospheric pressure of 780 millimeters 'of mercury. The invention is 'I'he terminals 5 and 8 of the condenser l and the terminals 'I and Il of the ionization chamber Il are-connected the'electrodes of a neon lamp Il. This lamp may contain neon or other gas under suitable low pressure. so that the striking voltage of said lamp I0 is about 80 volts. After the lamp Il has been struck, -current can be sent through said lamp at a voltage which is less than the striking voltaire.A The lamp I II is therefore an example of a resistance which has a falling characteristic. This type of resistance is sometimes designated as a negative resistance. 1

When the voltage at the terminals Ii, 6,'which is the same as the voltage between points 'I and Vco 9. exceeds volts, the' condenser-'4 will charge through said lamp Il.

The ionization chamber u is provided with o' suitable quantity of radio-active substance, so that the initial maximum ionization current between the electrodes E is, for example, 0.8 microampere.

The lamp Il is connected in parallel with the gap 50a, between the points 'I and I, so that the potential diiference which is applied to lamp Il, is the potential difl'erencel between the points I and -9. v i

This potential differencey between points 'I and 9 depends upon the ratio of the resistance of gap 50a, to the sum of the resistance of. sai-d gap lla and the resistance of resistor I I. Hence, when the resistance of gap 60a is the initial minimum resistance, the potential difference between points 'l and 9 will be only about 20 volts,'so thatthe initial voltage drop in resistor II willbe 80 volts. As the ionization current diminishes, as indicated by curve I2 of Fig. 6, and the resistance of gap 50a therefore increasesfthe difference of potential between points I and 9 will increase to the striking voltage, after a predetermined period of time which is regulated by the resistance of the resistor II, and the rate of decay of the radio-v active substance, with the resultant increase of space resistance of gap 50a. For example, if radon is used as the radio-active material, the voltage which is applied to lamp IIIv may b'e equal to the striking voltage, at the expiration of a delay period of eight days. I'he circuit of lamp I0 includes an electric fuse Il, which may be replaced by any device which is to be operated or energized by the electric current which is passed through lamp I0.

In using the embodiment.I of Fig. 1, the source I is connected to lamp I0, only after the gap Ita has been suillciently ionized to prevent the immediate striking of said lamp Il.

The discharge energy in this embodiment of Fig. 1 is small, unless a large condenser l is used, so that for many purposes it would be necessary to use a condenser of much larger capacity than as above stated.

.The circuit of Fig. 2 makes it possible to secure much greater discharge energy through the fuse Il or other device. This circuit contains a second neon lamp Ia which is similar to the lamp II. In the embodiment of Fig. 2i, the voltage between the terminals 2 and 3 of the series-connected dry cells I is about volts, if the striking voltage of lamp Ill is 80-volts.` One terminal of the auxiliary lamp Ia is connected through the fuse orother device Il, to a point I5.of .the seriesconnected dry cells, so that the voltage between the points Ii and 3 is a suitable fraction of the total terminal voltage between the terminals 2 and 3. The voltage between the points I5 and 3 is sumcient to maintain a current through lamp Ilia, after said lamp Ita has been struck. Said voltage between points I5 and 3 is less than said striking voltage.

The circuit of the lamp III includes a primary transformer coil or inductance I6, which is in-" ductively coupled to a secondary transformer coil or inductance I1. The transformer IC-I'I is a step-up-transformer. The number of turns in the coil IS is about 2%% of the number of turnsin the coil I1, and the inductive coupling between said coils I6 and I1 is very close. Hence, when the condenser l discharges through said lamp I0 and inductance II, sumcient voltage will be induced `in coil l1 to strike lamp Ila. The

ously stated, the condenser 6 will discharge through the lamp la, only after a predetermined period of time has elapsed. Lamp Illa will be struck by said discharge. by means of the transformer. Current from source I is then passed through the lamp Ida, until the explosion or other desired eiect takes place. The current which can thus be sent through the fuse or other device I6, which is in the circuit of lamp |041, can be from 10-20 milliamperes if an ordi'- nary small sized neon lamp lila is used. By using a well-known special type of neon lamp, said current which is sent through the lamp Illa from source I can be as large as milliamperes. The power which is thus made available by the relay can be approximately a watt, which is sumciently great to produce the explosion or other desired result.

In the examples above given, we have described the use of a radio-active substance which begins to decay as soon as it is introduced into the ionization chamber, so that the period o.' delay of the action of the relay, begins from the time when such substance is introduced' into said ionization chamber.

However, we can also use any radio-active substance which will continuously emanate radon. Radium has a very long half-life period of about 2000 years and a given quantity of radium will produce a continuous supply of radon. Said radon is a. gas which will accumulate in a closed ionization chamber up to 'a maximum equilibrium limit, because one half of the radon disintegrates during a period of approximately four days. Hence, when this limit is reached, the rate of supply of radon will be equal to its rate of decay.

We can therefore introduce radium or a ra.- dium alloy or compound into the respective ionization chambers 50 of the embodiments of Figs. l and 2, thus producing a constant ionization current which will not diminish. The relay can be primed by removing the radium or the like from said ionization chamber, thus starting the period of decay of the radon and the increase in resistance ofgap 50a.

The radium can be removed either manually or automatically in the case of an aerial bomb, when the bomb is dropped. We have not illustrated simple conventional mechanisms for removing a plug which contains the radium from said ionization chamber when the bomb is dropped, because such conventional devices form no part of our invention per se.

We can also subject the gap 50a to ionization from any source, so that the ionization will stop immediately whenv the action of such source is discontinued. Such source may be Roentgen rays, ultra-violet light or the like. For example, if the circuit of the Roentgen ray machine is opened, the resistance of gap 50a will rise rapidly, thus causing a very rapid operation of the relay. Hence -the invention is not limited to the use of any particular ionizing means, or to the location of the same in the ionization chamber 50. I Fig. 3 diagrammatically shows a carrier I8, one face of which is provided with a layer Ra of radium or radium alloy or radium compound. Fig. 3 also sho'ws the use of a pairvof ionization chambers 50 and 50h, which may be identical.

f These ionization chambers have respective pairs ot electrodes Ea and E, which have respective gaps Il and B2. The preferred physical construction oi' the embodiment of Fig. 3 is shown in Fig. 4, which shows that .the ionization chambers are connected by an intermediate tube, and that the carrier Il is a turnable valve, which closes said intermediate tube, so as to prevent the passage o! gas between said ionization chambers. Hence. if the solid layer Ra is radium or a radium compound or radium alloy, which yields radon, the supply of said radon can be limited only to one of said ionization chambers. If the layer Ra is o! the aforesaid type, radon will be supplied only to the ionization chamber 50h, when the carrier I0 is in the non-priming position which is shown in Fig.' 4. andsaid radon will be accumulated in chamber 50h, up to a maximum limit at which the rate of decay will equal the rate of supply. While carrier I8 is in said nonpriming position, the circuit of lamp Ill will be open, because of the very high resistance of gap M.

In order to prime the device, carrier I8 is turned through an angle of from the position shown in Fig. 4. in order to supply radon tochamber 60 and to discontinue the supply of radon to chamber 50h.

The resistance of gap 5I will therefore diminish at a rate which corresponds to the increase of ionization which is designated by curve I9. The resistance of gap 52 will simultaneously increase at a rate which corresponds to the decrease of ionization current which is designated by curve I2. At the point P, the resistances of said gaps 5I and 52 will be equal, and the respective voltage drops through said respective gaps willbeequal.

The ordinate OP represents said equal ionization currents. i

Alter the device of Fig. 3 and Fig. i has been thus primed, the voltage which is applied tothe lamp Ill is the diierence of potential between points 20 and 2l. The resistance between points r 20 and 2| will progressively increase, while the resistance of gap 5I will simultaneously progressively decrease. Hence the voltage between points 20 and 2| will increase to the striking voltage, after a predetermined period of time. The condenser 4, which will then be charged to the striking Voltage, will then discharge through lamp I0 and primary coil IB. This will strike lamp Illa, by means of the transformer, and lamp Illa will then receive a steady current from the source I, untilthe electric fuse I4 or other device has been operated. y A

The embodiment of Fig. 3 eliminates the use of the high resistance II, which is desirable, because such high resistances vary with variations in temperature. The embodiment of Fig. 3 also diminishes the eiect of variations in the voltage of the dry cells, which may result from changes in temperature or the lapse of time.

The potential diierence between the points I5 and 3 is sufcient to maintain the current through the lamp Illa, after said lamp has been struck, as in Fig. 2. f

V In the embodiment of Figs. 1-3, the walls or envelopes of the chambers 50, 5017 are made of glass or other non-conductive material.

In the embodiment 0f Fig. 4,.we use a pair of chambers 22 and 22a which have conductive metal walls which are iixed to the connecting tube 23, whose wall is also made Y of conductive metal. Hence the walls of chambers 22 and 22o and the position, the supply of radon to chamber 22a is commenced, and the supply ofgradon to chamber 22 is stopped. The internal space resistance of chamber 22a will progressively decrease. while the internal space resistance of chamber 22 is simultaneously increased.

Each said chamber 22 and 22a has its internal electrode located centrally with respect to its metal wall, which is of closed spherical shape save for the opening of tube 22.

When current initially' flows from the internal electrode of chamber 22a throughr the space oi' said chamber 22a to its'metal wall, a part of said current will ilow through the metal wallof tube 22 to the metal wall of chamber 22, through the ionized filling of chamber 22 to its respective internal electrode, and to point lll of the circuit. Hence the voltage which is applied to lamp or tube I lwill be less than the striking voltage of said lamp or tube I0, until the internal resistance of chamber 22 will increase to a predetermined limit. At the end of a predetermined delay period, the condenser 4 will be charged to the striking voltage, and said condenser l will discharge through lamp I0 and primary coil I8, thus striking lamp Illa. The carrier Il can be held in asvaiso j wallottube22erselectricallyconnectedtoescl:l voltageoiseidlsmpILbutthes/sidiampll other. 'Ihecarrierilisshapedlikeavalvaso centhenbedruckattheendotsperiodwnieh that it always separatestherespective gaseous islessthanihemaximumperiodoideiay.'laid niiingsofthechambers22end22a.inallposi periodotdelaycsnbevesyshort. tionsotssidcarrierllfaidcanierilispreb .i'hisstrikingcanliesecuredwhentiieiilllugsA erabiymadeofglassorothernon-conduetivema'- oi the tubes 22 and22aareequallyionissd,es teriahbutwearenotlimitedtoanyparticular illustratedbythepointoiintersectionos'the material. Thepositionoi'thecarrierllwhichis curvesi2andi2inlig.0. showninilig.4,isthenonprimingposition. vIn 'l'hetotlimistbesemeinoonsuchnon-primingpositiomthelayei-Raoiradiom structionsnd operation ss the oi active material supplies radononlytothechaml'igs.8and4,s avethattheoi!lg.5 ber 22. Each said chamber 22 and 22a has a has two identical oondenssrslband la. singleinternalelectrodawhichisseparatedrrom WhencarrierIIisinthenon-primingposition the respectivemetalwallbyinsulation 24. oill'ig 5,thecircuitotthe'sourceiisopen,since Inthenon-primingposiidcnofllig 4.radonis l5 gap li lemon-conductivasavethatatnnsient supplied only to chamber 22, and the nlling of chusma currentwilileak condenando, chamber 22a remains non-ioniaed Hence the and there may be aslight leakage current. '111e circuit ofsourceiremainsopen. because theinterminals ci condenserlaareconnectedtothe ternal electrode of chamber 22aisinsulated trom circuitatpoints ll and Il, endpoint I2 hesthe the metal wall oi' said chamber. While carrier 20 same potential ss point Il.' Hence, whilesome i2 is held in said non-priming position. radon is current iiows through condenser lb and gap I2, accumulated in chamber 22, either up to or less while carrier i2 is in said non-priming position, than the maximum possible accumulationofsaid thelamp Ilwillnotbestruckbecausethevoltradon. l agedropbetweenpoints 22andliwillbeless Whenthecarrierltisturnedtothepriming thanthestrikingvoltage. Whilethecarrierll is in said non-pruning position, the condenser la tion.andtlieresisienceoigapllhasbeensudtcientlyloweredandthereslstanceoigaphas been sumeiently increased. the lamp Il will be struck and the condenser la will discharge through lamp il and inductance ll, in an oscillatory or non-oscillatory discharge, Athus striking lamp Ils. While condenser la is thus discharged.

lthel charge of condenser 4b will increase;

.0 Iheruseorotherdevxce u'canbeomitted, so

that the lamp il or Ila will be the which is operated.

" In each embodiment, we utilise a source of current whose circuit includes a" discharge element only element 5 which has s. mung cnn-mutisme wmcnrhss its non-priming position during a. relatively short period, so.v that the iilling of the chamber 22 will be ionize'dless than the maximum, before the..

carrier I8 is turned to the priming position In each of the embodiments, the circuit can be provided with a. conventional manuallyv operated switch. The valve chamber in 'which carrier il is located, can have an opening, so that when lcarrier I8 is turned counterclockwise through an 'the ionization of the iilling of chamber 22 will be less than the maximum, and the supply of radon to chamber 22 will be less than the maximum. When carrier i8 is then turned to the priming position, the initial voltage which is applied to lamp Iii will be less than the striking a predetermined striking voltage. The voltage ot said source exceeds said striking voltage; Baid circuit has a shunt which is connected to slid .circuit across the terminals of said discharge element. Said shunt has a pair of spaced electrodes whose gap has an ionizable gas, or ionizable vpor as an equivalent. Hence the voltage which is applied to said discharge element is the voltage which is applied across said shunt. Said gas is ionized by radon or other radio-active material, so that when said ionization exceeds a predetermined minimum, the voltage across said shunt is less than said striking voltage. In addition, and as an optional element, a capacitance is connected to said circuit in parallel to said discharge ele-V ment. so that the voltage which is applied to said capacitance exceeds said striking voltage,

.only when the voltage across said shunt exceeds said striking voltage. This capacitance, if used,

is connected to the terminals of said discharge element independently of said gap, so that the discharge current of said capacitance does not pass through said gap.

The use of a capacitance is desirable in order to produce-'a short and strong current pulse by the discharge o! said capacitance when the strik-v main circuit in which said capacitance is located. even if said main circuit is not coupled to an auxiliary circuit which has an auxliary dicsharge element. The main circuit can be coupled to said auxiliary circuit in any manner, instead of using the inductive coupling which is disclosed herein, as one type of such coupling.

The ionizing means which are mentioned in the claims may be radon, other radio-active material or other source of ionizing energy.

Fig. 7 shows the substitution of a photoelectric cell R for the ionization chamber 50 of Fig. 2. Said cell R has a. cathode C of caesium or the like, which is connected to point 1 of the circuit and to the negative terminal 2 of the source of current I. The anode of said cell R is connected to point 9 and to the positive terminal 3. Said cell R has the usual window W. When light is excluded from window W, said cell R has high resistance, so that lamp i is subjected to the striking volatge. While the cathode of said cell R is energized by light so as to emit electrons, the resistance of cell R is suilciently low so that lamp id is not struck. Hence the relay device of Fig. 7 is operated only when light is excluded from said cell R. We can use anyv type of photo-electric cell, which operates at ordinary temperature. Photo-electric cells can be substituted in the other embodiments. For example, in the embodiment of Fig. 3, the ionization chamber 50 can be replaced by a photo-electric cell which normally receives no light and ionization chamber 50h can be replaced by a photo-electric cell which normally receives light. This relay may be operated by operating respective shutters or by changes in light intensity so as to subject the cathode ofl the photo-electric cell which replaces chamber 50 to light or to variations in intensity of light, and excluding light from the cathode of the photo-electric cell which replaces chamber 50h, or changing the intensity of the light on the respective cathode. Such a relay may operate rapidly.

Strictly speaking, the space current of a highly evacuated photo-.electric cell is an electronic current instead of an ionization current. Such a photo-electric cell may have suillcient residual gas, so that its space current is increasedvby ionization. The use of a photo-electric cell or cells of the cold type is within the scope of the invention. However, we greatly prefer the use v of radio-active material, as distinguished from all other means for securing a space current.

In the embodiment of Fig. 4, each ionization chamber 22 and 22a has a pair of spaced electrodes, since the metal wall of each said chamber constitutes an electrode.

The ionizable material in the gaps between the electrodes of the ionization chambers, and the cathode of the photo-electric tube, are generally charge element ita, as a matter of convenience. In the embodiment illustrated in Fig. 2. for example, the part of battery I between Il and I could be replaced by another source of current. whose voltage is below the striking voltage of the discharge element Ica. In each embodiment, the ultimate current-consuming device Il is directly connected to a respective source o! current through a discharge element I0 or lila which has a falling characteristic, so that the respective discharge element i0 or 10a is connected in series with device Il, and the respective discharge velement i0 or i0a directly blocks the supply of current to the ultimate current-consuming device |4 until said discharge element is struck. Figs. 2. 3, 4, 5, and 7, each show a single eflective circuit, which has one or more branches. Each said circuit has a control shunt which controls the application of the striking voltage across the respective discharge element i0 or Illa. Each said control shunt includes a radiation-responsive element and additional independent resistance.

We claim:

1. In combination, a source of current, a circuit whose terminals are connected to said source of current, an ultimate current-consuming device located permanently in said circuit, a discharge element connected in said circuit in series with said ultimate current-consuming device, said discharge element having a falling characteristic and requiring a striking voltage which exceeds its operating voltage after it has been struck, said discharge element directly blocking the passage of current through said ultimate current-con suming device until said discharge element has been struck and permitting the passage of current through said ultimate current-consuming device after said discharge element has been struck, -said circuit having a control-shunt which controls the application of striking voltage across said discharge element, said circuit having resistance additional to the resistance of said shunt, said control shunt having electrodes which are separated by a gap in which anionizable gas is located so that the resistance of said shunt is decreased by increased ionization of said gas, said additional resistance being sumciently high so that said control shunt blocks the application of striking voltage to said discharge element as long as the resistance of said ionizable gas in said gap is below a predetermined limit, and a source of radiation for ionizing the gas in said gap.

2. In combination, a source of current, a circuit connected to the terminals of said source, a discharge element located in said circuit, said discharge element having a falling characteristic and a striking voltage and an operating voltage which is less than said striking voltage after said discharge element has been struck, the voltage of said source exceeding said striking voltage, a primary coil of a transformer connected in series with said discharge element, a control shunt connected in said circuit across said discharge element and said primary coil so that the voltage which is applied across said discharge element and said primary coil is the voltage which is l applied across said control shunt, said control shunt including spaced electrodes which are septo said circuit in parallel relative to said discharge element and said primary coil. said capacitance being connected to said discharge element and said primary coil independently 'of saidVv gap, the voltage o: said capacitance exceeding said striking voltage only when the voltage across said shunt exceeds said striking voltage, said circuit including a branch which has a secondary coil which is inductively coupled to said primary coil, said branch inc uding an auxiliary discharge element of the oresaid type which is connected in series with said secondary coil, said branch being connected to a source of current whose voltage is less than the striking voltage oisaid auxiliary discharge element and which exceeds the operating voltage of said auxiliary discharge element.

3. In combination, a source of current, a circuit connected to the terminals of said source. a discharge element located in said circuit, said discharge element having a falling characteristic and a striking voltage and an operating voltage which is less than said striking voltage alter said discharge element has been struck, the voltage of said source exceeding striking voltage, a primary coil of a transformer connected in series with said discharge element, a control shunt connected in said circuit across said discharge element and said primary coil so that the voltage which is applied across said discharge* element and said primary coil is the voltage which is applied across said control shunt, said control shunt including spaced electrodes which are separated by a gap in which ionizable gas is located, so that the resistance or said control shunt is decreased by increased ionization of said gas, a source of ionization for ionizing the gas in said gap, the voltage across said shunt being less than the striking voltage when said gas is ionized above a predetermined limit, a capacitance connected to said circuit in parallel relative to said discharge element and said primary coil, said capacitance being connected to said discharge element and said primary coil independently of said gap, the voltage oisaid capacitance exceeding Said striking voltage only when the voltage across said shunt exceeds said striking voltage, said circuit including a branch which has a secondary coil which is inductively coupled to said primary coil, said branch including an auxiliary discharge element of the aforesaid type which is connected in series with said secondary coil, said branch being connected to a source of current whose voltage is less than the striking voltage of said auxiliary discharge element and which exceeds the operating voltage of said auxiliary discharge element,-said gap having radon associated therewith in order to ionize said gas.

4. In combination, a source of current, a cirasunto which en ienisabie su is located, se um the resistance o! said control shuntls decreased by increased ionization o! said gas, said control shunt blocking the application o! striking volte age to said discharge element as long as the resistance ot said ionizable gas in said gap is below a predetermined limit, a second shunt which includes a capacitance whose terminals are connected to the terminals of said control-shunt so that the voltage of said capacitance is equal to the voltage-applied across said shunt, and means for ionizing the gas in said gap.

5. In combination. a source of current, a circuit whose terminals are connected to said source oi current, an ultimate current-consuming device located permanently in said circuit, a discharge element connected in said circuit in series with said ultimate current-consuming device, said discharge element having a falling characteristic and requiring a striking voltage which exceeds its operating voltage after striking, said discharge element directly blocking the passage oi' current through said ultimate current-consuming device until said discharge element has been -struck and permitting the passage ot current through said current-consuming device alter said discharge element has been struck, said circuit having a control shunt 'which controls the application of striking voltage across said discharge element, in accordance with the voltage drop across said shunt, said control shunt having a gap through which space current can be sent, sini; gip inecliding radiationyresponsive means so a er tanceoflsaidshuntispro to the intensity o! the radiation which um by said radiation-responsive means, a vsource ot radiation for said radiation-responsive means, said circuit having resistance independent oi said shunt so that the applied voltage across said I shunt is proportional to the ratio of the resistance cuit whose terminals are connected to said source current, an ultimate current-consuming device located in said circuit, a discharge element connected in said circuit in series with said ultimate current-consuming device, said discharge element having a falling characteristic and requiring a predetermined striking voltage which exceeds its operating voltage after striking, said discharge element directly blocking the passage of current through'said intimate current-consuming device until said discharge element is struck and permitting the passage of current through said ultimate current-'consuming device after said discharge element is struck. said -circuit having a control-shunt which controls the of said shunt to the sum of the resistance of said shunt and of said additional resistance, said control shunt blocking the applicationgor said striking voltage as long as its resistance is below a predtermined limit.

6. In combination, a source oi' current, a circuit whose terminals are connected to said source or current, an ultimate current-consuming device located in said circuit, a discharge element connected in said circuit in series with said ultimate current-consuming device, said discharge element having a falling characteristic and requiring a striking voltage which exceeds its operating voltage after it has been struck, said discharge element directly blocking the passage of current through said ultimate current-consuming device until saidV discharge element has been struck and permitting the e ot current through said current consuming device alter said 'discharge element has been struck, said circuithaving a control ahunt which controls theapplicatiorn of striking voltage .across said discharge el'ement according to the voltage drop across said control shunt, said shunt having a nrst radiation-responsive resistor therein, said circuit having a second radiation-responsive resistor between. one end of saidsource and one endo! said control shimt,

the resistance or each radiation-responsive resistor being in proportion to the radiation received thereby, radiation-supplying means adapted to control the respective ot said respective radiation-responsive resistors, said control shunt blocking the application of striking voltage across said discharge element as 'long as the resistance of its radiation-responsive resistor is below a predetermined proportion of the resistance of the second radiation-responsive resistor.

7. A combination according to claim 6, in which the primary coil of a transformer is connected in series with said dischargeelement, said ultimatecurrent consuming device being located in a branch of said circuit, said branch including the secondary coil of said transformer and a, second discharge element of the aforesaid type which is connected in series with said ultimate currentconsuming device, said branch having a source of current Whose voltage is less than the striking voltage of said second discharge element and equal to the operating voltage of said discharge element.

FRANCIS PERRIN. BORIS PREGEL. 

